HOK Group, Inc., formerly Hellmuth, Obata + Kassabaum, is an American design, architecture, engineering, and urban planning firm. Founded in 1955, it is headquartered in St. Louis, Missouri.
History
Founding HOK was established in St. Louis, Missouri, in 1955. The firm is named for its three founding partners: George F. Hellmuth, Gyo Obata and George Kassabaum, all graduates of the School of Architecture at Washington University in St. Louis.
The practice's first building designs were schools in St. Louis suburbs, and St. Thomas Aquinas High School in Florissant was the first independent school designed by the firm. Another prominent school they designed was the Saint Louis Priory School.
Early years By the mid-1960s, the firm began to open additional offices, starting with San Francisco in 1966 for the design of a library at Stanford University and Dallas in 1968 for the master planning and design of Dallas/Fort Worth International Airport. Also in 1968, HOK launched its interior design practice. That year, HOK expanded into Washington, D.C., after winning the commission to design the Smithsonian National Air and Space Museum. In 1973, HOK established a presence in New York by acquiring Kahn & Jacobs, designers of many New York City skyscrapers. By the 1970s, the firm was operating internationally and in 1975 the firm was named as architect of the $3.5 billion King Saud University in Riyadh, at the time the single largest building project in the world. In 1979, George Kassabaum was elected into the National Academy of Design as an Associate Academician.
In 1983, HOK formed HOK Sport Venue Event, a subsidiary devoted entirely to designing sport stadiums, arenas, and convention centers, an architectural boom market at the time. In January 2009, the Board of HOK Group, Inc. and managers of HOK Sports Facilities, LLC transferred ownership of HOK Sport to leaders of that practice. The company became an independent firm, and rebranded itself as Populous.
Expansion and acquisitions HOK's first office outside the US opened in Hong Kong in 1984, and the second in London in 1987, a practice that would be expanded in 1995 by merging with the British architectural practice Cecil Denny Highton.
The firm expanded into China in 2013, when it acquired the New York and Shanghai offices of hospitality design firm BBG-BBGM, creating one of the world's largest interior design firms, although BBG-BBGM's office in Washington, D.C., continues to operate as BBGM. By 2007, international work represented more than 40% of HOK's annual revenue.Staff (June 23, 2008) "Uncertain Economy Pushes Design Firms To Diversify Their Portfolios" Engineering News-Record
As of July 2026, HOK operates 28 offices across North America, Europe, and Asia, including in Hong Kong, Beijing and Shanghai in China; Dubai in the Middle East; Mumbai, India; and Toronto, Canada, where it established its first offices in 1997 with the acquisition of Urbana Architects.
Other domestic acquisitions include Caudill Rowlett Scott based in Houston, Texas, in November 1994, adding offices in Houston and Atlanta. The purchase of 360 Architecture in January 2015, a 200-person, Kansas City-based firm, gave the group additional capabilities in the design of stadiums, ballparks and arenas. That acquisition enabled HOK to launch a new global Sports, Recreation, and Entertainment design practice after the breakaway of Populous, and to open new offices in Kansas City and Columbus, Ohio (which has since closed). In May 2026, HOK acquired Rossetti Architects, a Detroit-based architecture firm.
On May 15, 2015, the firm announced a multi-year partnership with the United Soccer League (USL) in the US to lead a stadium development, design, and standards initiative to help house all USL clubs in soccer-specific stadiums across North America by the end of the decade.
Leadership In 2023, Eli Hoisington and Susan Klumpp Williams were appointed joint co-CEOs of HOK, the firm's youngest CEOs, and the first time it had appointed a woman. They succeeded Bill Hellmuth, founder George Hellmuth's nephew, who was president of the firm from 2004 to 2016 and CEO from 2016 until his passing in 2023. Prior to Bill Hellmuth, Patrick MacLeamy served as HOK's CEO from 2003 to 2016, and chairman since 2012. MacLeamy succeeded HOK chairman Bill Valentine when he retired after 50 years with the firm.
Design philosophy In 1983, HOK introduced HOK Draw, computer-aided drafting software products that specialized in conceptual architectural design. In the early 2000s, HOK began using Building Information Modeling (BIM) to streamline the design and construction process.Staff (January 30, 2007) "BIM at HOK", AEC Magazine January 30, 2007.
His team designed the Weather Prediction Center with a four-story waterfall to direct rainwater into bio-retention gardens; and a louvred sunlight system for a building used by the Office of the Chief Medical Examiner.
HOK has worked with the Biomimicry Group, co-founded by Janine Benyus, since 2008, which directs designers to use natural models in solving problems such as precipitation capture.Merchant, Brian (September 22, 2009) "HOK and Biomimicry Guild Forge Alliance for Bio-Inspired Design Excellence" TreeHugger In 2010, they collaborated with the energy and daylight consultancy, The Weidt Group, to complete Net Zero Court, a zero-emissions class A commercial office building in St. Louis.Valentine, Bill (October 2010) "Net Zero: Two global design firms issue a call to action and lead by example" , Contract Using an ocular roof design, their 2017 Mercedes-Benz Stadium became the first LEED Platinum certified sports stadium in the US. Their design for the Boston Consulting Group HQ in Toronto in 2022, uses principles of wellness-informed architecture, to maximize natural light and encouraging standing.
Publications
Selected projects 1962: The Priory Chapel, St. Louis, Missouri, United States 1970: Houston Galleria, Houston, Texas, United States 1970: Xerox PARC, Palo Alto, California, United States 1975: King Saud University, Riyadh, Saudi Arabia 1976: National Air and Space Museum, Washington, D.C., United States 1977 Hulen Mall, Fort Worth, Texas, United States 1979: Cecil H. Green Library, Stanford University, Stanford, California, United States 1980: Dulles International Airport Main Terminal expansion, Dulles, Virginia, United States 1981: Moscone Center, San Francisco, California, United States 1981: Metropolitan Square, St. Louis, Missouri, United States 1982: Levi's Plaza, San Francisco, California, United States 1983: King Khaled International Airport, Riyadh, Saudi Arabia 1985: St. Louis Union Station Renovation and Redevelopment, St. Louis, Missouri, United States 1986: BP Building Cleveland, Ohio, United States 1986: Kellogg Company Headquarters Battle Creek, Michigan, United States 1986: Riverchase Galleria Birmingham, Alabama, United States 1991: 801 Grand, Des Moines, Iowa, United States (tallest building in Iowa) 1992: Schapiro Center for Engineering and Physical Science Research (CEPSR), Columbia University, New York City, United States 1993: Apple Inc. R&D Campus, Cupertino, California, United States 1994: Independence Temple, Independence, Missouri, United States 1995: Tokyo Telecom Center, Tokyo, Japan (co-designers) 1996: Tuntex Sky Tower, Kaohsiung, Taiwan 1996–1997: Nortel Brampton Centre HQ, Brampton, Ontario, Canada 1997: Foreign and Commonwealth Office Restoration, London, England 1997: George Bush Presidential Library, College Station, Texas, United States (on the campus of Texas A&M University) 1999: Northwestern Memorial Hospital Facility Replacement and Redevelopment, Chicago, Illinois, United States (co-designers) 1999: Edificio Malecon Office Tower, Buenos Aires, Argentina 1999: Boeing Leadership Center, St. Louis, Missouri, United States 1999: American Airlines Arena (home of NBA's Miami Heat), Miami, Florida, United States 2000: Passenger Terminal Amsterdam, Amsterdam, Netherlands 2000: Nationwide Arena (home of NHL's Columbus Blue Jackets), Columbus, Ohio, United States 2001: United States Environmental Protection Agency Research Center, Research Triangle Park, North Carolina, United States (1.2 million-sq.-ft. campus) 2002: Darwin Centre at the Natural History Museum, Passenger Terminal Cork, Cork Airport, Ireland 2002: Alfred A. Arraj U.S. Courthouse, Denver, Colorado, United States 2003: Steven F. Udvar-Hazy Center of the National Air and Space Museum, Chantilly, Virginia, United States 2004: Harlem Hospital Center Master Plan and Patient Pavilion, New York City, United States 2005: Cisco Systems Executive Briefing Center Interior Design, San Jose, California, United States 2005: Terminal A at Logan International Airport, Boston, Massachusetts, United States (world's first LEED certified air terminal building) 2005: Stockton Arena (home of ECHL Stockton Thunder), Stockton, California, United States 2006: Lavasa Hill Station Master Plan and Design Guidelines, Moss Valley, Pune, India 2006: Natural History Museum of the Adirondacks (The Wild Center), Tupper Lake, New York, United States 2006: SJ Berwin European Headquarters Interior Design, London, England, (Business Week/Architectural Record Award winner) 2007: Dubai Marina, Dubai, United Arab Emirates 2007: Hyatt on the Bund, Shanghai, China 2007: Sprint Center, Kansas City, Missouri, United States 2008: Frost Art Museum, Florida International University, Miami, Florida, United States 2008: Midfield Terminal at the Indianapolis International Airport, Indianapolis, Indiana, United States (master designer) 2008: Kansas City Power & Light District, Kansas City, Missouri, United States 2009: Doha City Centre, Doha, Qatar, (design of five hotel towers for largest retail development in the Middle East) 2009: King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia (Saudi Arabia's first LEED certified project and the world's largest LEED Platinum project) 2009: Carnival House, head office of Carnival UK, Southampton, England 2009: Bakrie Tower, Jakarta, Indonesia 2009: Huntington Park (home of Triple-A MiLB Columbus Clippers), Columbus, Ohio, United States 2010: Indira Gandhi International Airport – Terminal 3, Delhi, India (LEED Gold certification) 2010: New Building 20 at NASA's Lyndon B. Johnson Space Center, Houston, Texas, (LEED Platinum certification) 2010: MetLife Stadium (home of NFL's New York Giants and New York Jets), East Rutherford, New Jersey, United States 2011: Salvador Dalí Museum, St. Petersburg, Florida 2011: Brigade Gateway Enclave, Bengaluru, India 2011: Keangnam Hanoi Landmark Tower, Hanoi, Vietnam (tallest building in Vietnam) 2012: Canon USA Headquarters, Melville, New York 2012: Baku Flame Towers, Baku, Azerbaijan 2012: Harlem Hospital Center Mural Pavilion, New York City 2013: San Francisco Mint Adaptive Reuse, San Francisco, California 2013: BBC Broadcasting House Headquarters Workplace Strategy and Interior Design, London, England 2013: Husky Stadium (home of University of Washington football), Seattle, Washington, United States 2013: Auburn University Recreation & Wellness Center, Auburn, Alabama, United States 2014: 535 Mission Street, San Francisco, California, United States 2014: Anaheim Regional Transportation Intermodal Center, Anaheim, California, United States 2014: National Oceanic and Atmospheric Administration Inouye Regional Center, Pearl Harbor, Hawaii, United States 2014: Hamad International Airport Passenger Terminal Complex, Doha, Qatar 2015: PayPal Park (home of MLS's San Jose Earthquakes), San Jose, California, United States 2015: Porsche U.S. Headquarters and Customer Experience Center, Atlanta, Georgia 2015: University of Chicago William Eckhardt Research Center, Chicago, Illinois 2016: Abu Dhabi National Oil Company Headquarters, Abu Dhabi, United Arab Emirates